Determine the equation of the line that passes through the point (-2,1) and it is perpendicular to -x+4y-3=0

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giorgiana1976 | College Teacher | (Level 3) Valedictorian

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We'll write the equation of the line into the slope intercept form:

y=mx+n, where m is the slope of the line and n is the y intercept.

We need to put the equations in this form to determine their slopes. We'll use the property of slopes of 2 perpendicular lines: the product of the values of the slopes of 2 perpendicular lines is -1.

Let's suppose that the 2 slopes are m1 and m2.


We'll determine m1 from the given equation of the line, that is perpendicular to the one with the unknown equation.

The equation is -x+4y-3=0.

We'll isolate 4y to the left side. For this reason, we'll subtract -x - 3 both sides:

4y = x + 3

We'll divide by 4:

y = x/4 + 3/4

The slope m1 = 1/4.



We also know that the line passes through the point (-2,1), so the equation of a line that passes throuh a given point and it has a known slope is:



We'll remove the brackets and we'll move all terms to one side:

y - 1 + 4x + 8 = 0

We'll combine like terms and we'll get the equation of the requested line: y + 4x + 7 = 0